Nuclear magnetic resonance (NMR) is a well-known analytic technique that has been used in a number of fields, such as spectroscopy, bio-sensing and medical imaging. In general, an NMR device includes transceiver circuits to transmit signals to a tested sample and receive echo signals therefrom. The echo signals are then analyzed to obtain imaging and/or material information of the sample. The NMR echo signals, however, are typically very small (on the order of microvolts) and represent free induction decay; this can pose a considerable challenge to the NMR system. For example, the sensitivity of the NMR transceiver has to be sufficient in order to detect the small echo signals. In addition, the NMR transceiver has to amplify the received NMR signals to a level sufficient to permit processing for analysis.
Conventionally, the NMR transceiver includes an amplifier of a fixed gain for amplifying the detected NMR signals. Fixed-gain amplification, however, may not be sufficient to amplify the damped portions of the NMR decay signals to a desired level suitable for signal processing. In addition, fixed-gain amplification may result in saturation of the less-damped portions of the NMR signals, thereby providing inaccurate NMR analysis. Accordingly, there is a need for an approach that ensures the detected NMR echo signals, particularly the damped portions, are amplified to a level sufficient to permit analysis without saturation of the less-damped portions of the NMR echo signals.